Conventional information processing systems are often configured to encrypt messages that are delivered from one device of the system to another device of the system. However, these conventional systems can be problematic, particularly with regard to the enforcement of policies relating to message distribution and access. For example, in some conventional systems, a server that distributes encrypted messages to client devices has access to the cryptographic keys and therefore can decrypt the messages. This adversely impacts the privacy of the users that send and receive the encrypted messages.